Comparison of different mechanisms proposed to explain the onset of Northern Hemisphere Glaciation
Abstract
Different mechanisms have been proposed to explain the transition from the warm climate of the middle Pliocene to the following cold climate and the onset of glaciation in the Northern Hemisphere approximately 2.75 million years ago (Ma). The proposed mechanism include increased obliquity and eccentricity forcing (Maslim et al. 1998), reduced atmospheric CO2 concentrations (Mudelsee and Raymo, 2005), closure of the Central America seaway causing the strengthnening of the Atlantic Meridional Overturning Circulation and associated increased moisture supply to the areas of ice sheet formation (Haug and Tiedemann, 1998), increased seasonality in the North Pacific (Haug et al. 2005), and/or permanent El Ninno conditions prior to the transition at ~2.75 Ma (Wara et al. 2005). In this study these hypothesis are compared via simulations with an Atmospheric General Circulation Model coupled to a slab ocean model. The amplitude and spatial patterns of climate change associated to each hypothesis are analysed, and a Equilibrium Line Altitude calculation is used in order to evaluate the relevance of these signals for the initiation of ice sheets.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMPP51E..08V
- Keywords:
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- 0726 Ice sheets;
- 4922 El Nino (4522);
- 4928 Global climate models (1626;
- 3337);
- 4930 Greenhouse gases;
- 4934 Insolation forcing